This competing renewal application is for the Colorado Clinical Center of The Environmental Determinants of Diabetes in the Young (TEDDY) study. The primary objective of this multi-center, prospective cohort study initiated in 2003 is the identification of infectious agents, dietary factors, or other environmental exposures that trigger or protect against the development of islet autoimmunity and type 1 diabetes (T1D). Newborns are screened by HLA-DR,DQ genotyping to identify those at increased risk for T1D. Eligible children are followed four times per year until 4 years of age and twice a year thereafter until 15 years of age. Six Clinical Centers in the United States and Europe will screen 361,588 newborns and enroll 7,801 those eligible for prospective follow-up. The specific aims of this Clinical Center renewal application are to: 1. Complete this Center's contribution to the HLA-DR.DQ screening and enrollment of 7,801 high-risk infants into intensive prospective follow-up to achieve the overall TEDDY goals. 2. Refine strategies to retain subjects enrolled in the follow-up and collect all planned biological specimens and epidemiological data according to the standard protocol including close monitoring of performance and sample/data quality. 3. Ascertain prospectively development of islet autoantibodies and clinical T1D in the study subjects. 4. Perform planned laboratory tests at appropriate times using a nested case-control study design to answer specific scientific questions and hypotheses pertinent to the TEDDY study goals. 5. Analyze and publish laboratory and epidemiological data in collaboration with the TEDDY Data Coordinating Center (funded by a separate contract). 6. Guide the ongoing TEDDY project by participation of the Clinical Center investigators and staff in work of the study Steering Committee and sub-committees. A successful study outcome should allow better understanding of the etiology and pathogenesis of T1D and the development of new strategies to prevent, delay, or reverse the disease.